1. Field of the Invention
The present invention relates to the uses of tormentic acid in the inhibition of the activity of matrix metalloproteinase (MMP), inhibition of the expression of matrix metalloproteinase, inhibition of the phosphorylation of mitogen-activated protein kinase (MAPK), and/or promotion of the expression of collagen, especially in the improvement, repair, and/or care of skin.
2. Descriptions of the Related Art
Natural human aging processes include skin flaccidity, wrinkle formation and skin darkening, which gradually appear with aging. The layers of skin from top to bottom are the epidermis, dermis, and hypodermis. The causes of skin aging can be classified by endogenous and exogenous factors. Endogenous aging is a natural aging process of the human body, including cell apoptosis, hormone decrease, and weakened immunity. The decrease of hormone secretion may slow the metabolism of skin and gradually reduce the production of collagen and elastin because of the deterioration of the function of fibroblasts in the dermis. As a result, the connective tissues in the dermis degenerate, leading to flaccidity, and even wrinkling of the skin. Furthermore, the degeneration of connective tissues in the dermis may decrease the water storage (holding) function of the skin, leading to skin dryness and water deficiency, etc.
Exogenous aging is caused by extrinsic factors, such as sunshine, pollution, free radicals, and smoking. The main factor that damages the skin most and accelerates skin aging is ultraviolet (UV) rays from the sun. Depending on the wavelength, ultraviolet rays can be classified into long wavelength UV (UVA), medium wavelength UV (UVB), and short wavelength UV (UVC). Ultraviolet rays that people are most exposed to in daily life are UVA and UVB, which may cause erythema, sunburns, damage to the deoxyribonucleic acid (DNA) in skin cells, abnormality of the skin immune system, and skin cancer. The aging phenomenon caused by ultraviolet rays is called “photo-aging,” which may lead to an increase of matrix metalloproteinase (MMP) in the dermis via the phosphorylation of the mitogen-activated protein kinase (MAPK) pathway. Matrix metalloproteinase may decompose collagen in the skin. Without the support of collagen, the skin becomes flaccid, and cuticula may overgrow, leading to darkened and wrinkled skin.
Animal collagen that is currently known can be classified approximately into 21 types. Different kinds of collagen exist in different tissues. Out of all collagen in skin tissues, Type I collagen is the most abundant (80% of skin collagen) and has the most functions. Type III collagen comprises about 20% of the skin collagen. Fibroblasts in the dermis mainly produce Type I collagen and Type III collagen for the skin.
As described above, matrix metalloproteinase may decompose collagen and reduce the collagen content in the skin. Accordingly, if the MAPK Pathway or the activity and/or expression of matrix metalloproteinase in cells can be inhibited, the effects of improving/caring for skin quality can be achieved.
The inventors of the present invention found that tormentic acid has excellent effects of inhibiting the activity of matrix metalloproteinase, inhibiting the expression of matrix metalloproteinase, inhibiting the phosphorylation of mitogen-activated protein kinase, and/or promoting the expression of collagen, and thus it can be used for improving, repairing, and/or caring for the skin.